What is the Difference Between Presynaptic Neuron and Postsynaptic Neuron

The main difference between presynaptic neuron and postsynaptic neuron is that presynaptic neuron transmits electrical signals toward the synapse, whereas postsynaptic neuron transmits electrical signals from the synapse.

Presynaptic neurons and postsynaptic neurons are the two types of neurons that transmit nerve impulses to the synapse.

Key Areas Covered

1. What is Presynaptic Neuron
– Definition, Structure, Function
2. What is Postsynaptic Neuron
– Definition, Structure, Function
3. Similarities Between Presynaptic Neurons and Postsynaptic Neurons
– Outline of Common Features
4. Difference Between Presynaptic Neuron and Postsynaptic Neuron
– Comparison of Key Differences

Key Terms

Postsynaptic Neuron, Presynaptic Neuron

What is Presynaptic Neuron

The presynaptic neuron is the neuron that transmits nerve impulses toward the synapse. The nerve impulse is then converted into a chemical signal due to the secretion of neurotransmitters. It occurs at the synapse. A neuron is a signal-transducing cell that composes of three parts: cell body, axon, and dendrites. Here, the cell body contains the nucleus of the neuron cell. Metabolic events of the neuron occur in the cell body. Therefore, most neurotransmitters that release at the synapse are synthesized in the cell body. On the other hand, dendrites are small projections from the cell body, receiving the incoming nerve impulses and relaying them into the cell body. In the cell body, nerve signals are integrated to create a response.

Figure 1: Synapse

Furthermore, the axon is the outflow tract of the neuron. It is a cylindrical tube supported by neurofilaments and microtubules. Here, microtubules transport neurotransmitters through the axon to the axon terminals in order to release them into the synapse. Therefore, axon terminals of the presynaptic neuron occur at the synapse. Also, the main function of the presynaptic neuron is the transmit nerve impulses to the synapse.

Moreover, at the synapse, axon terminals of the presynaptic neuron release neurotransmitters into the synapse. These neurotransmitters stimulate various target organs.  

What is Postsynaptic Neuron

The postsynaptic neuron is the type of neuron that transmit nerve impulses from the synapse. Here, the synapse is the site of transmission from the presynaptic neuron to the postsynaptic neuron. Also, the synapse is the site that permits a neuron to transmit to the target neuron. Besides, a synapse composes of the pre-synaptic membrane, synaptic cleft, and post-synaptic membrane. Pre-synaptic and post-synaptic membranes are the two ends of membranes of the pre-synaptic and post-synaptic neurons, respectively.

Figure 2: Synapses Types

Moreover, there are six types of synapses according to the structures in the synapse. They are axosecretory, axoaxonic, axodendritic, axoextracellular, axosomatic, and axosynaptic synapses. Here, axosecretory synapses contain axon terminal secretes directly into the bloodstream. In the axoaxonic synapses, the axon terminal secretes into another axon. Whereas, in the axodendritic synapses, axon terminals end on the dendrite spine. Meanwhile, in the axoextracellular synapse, the axon secretes neurotransmitters, without any connection, into the extracellular fluid. However, in axosomatic synapses, axon terminal ends on soma. Finally, in the axosynaptic synapses, the axon terminal ends on another axon terminal.

Similarities Between Presynaptic Neurons and Postsynaptic Neurons

• Presynaptic neurons and postsynaptic neurons are the two types of neurons that involve in signal transduction.
• Both occur in the synapse.
• Their function is to transmit signals through neurons.

Difference Between Presynaptic Neuron and Postsynaptic Neuron

Definition

Presynaptic neuron refers to a neuron (nerve cell) that fires the neurotransmitter as a result of an action potential entering its axon terminal, while postsynaptic neuron refers to a neuron (nerve cell) that receives the neurotransmitter after it has crossed the synapse.

Occurrence

Presynaptic neuron occurs before the synapse, while postsynaptic neuron occurs after the synapse.  

Function

Presynaptic neuron transmits electrical signals toward the synapse, while postsynaptic neuron transmits electrical signals from the synapse.  

In the synapse

The presynaptic neuron is the signal-passing neuron, while the postsynaptic neuron is the target neuron.

Conclusion

In brief, the presynaptic and postsynaptic neurons are two types of neurons that occur in the synapse. Their function is to transmit nerve impulses. The presynaptic neuron occurs before the synapse. Also, it transmits nerve impulses toward the synapse. The axon terminals of the presynaptic neuron occur in the synapse. Whereas, postsynaptic neuron occurs after the synapse. However, it transmits nerve impulses from the synapse. Also, dendrites of the postsynaptic neuron occur in the synapse. Therefore, the main difference between presynaptic neuron and postsynaptic neuron is their structure and function.

References:

1. Caire MJ, Reddy V, Varacallo M. Physiology, Synapse. [Updated 2023 Mar 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. 

Image Courtesy:

1. “Synapse figure.” By Curtis Neveu – Own work (CC-BY SA 4.0) via Commons Wikimedia
2. “Blausen 0843 SynapseTypes” By BruceBlaus – Own Work (CC-BY 3.0) via Commons Wikimedia